Thin, flexible batteries, in which some but not all of the components are printed, are known. For example, in U.S. Pat. No. 5,652,043, a thin flexible battery is made by printing some of the components. This battery is not completely printed because it requires a porous insoluble substance as part of its aqueous electrolyte layer. That aqueous electrolyte layer comprises a deliquescent material, an electro-active soluble material and adhesive (or water soluble polymer) for binding the electrodes to the electrolyte layer, and the porous insoluble substance. The porous insoluble substance is described as filter paper, plastic membrane, cellulose membrane, and cloth. The negative and positive electrodes are then printed on either side of the electrolyte layer. Conductive layers of graphite paper or carbon cloth may be added over the electrolytes. Terminals, applied by printing, may be included in the battery.
U.S. Pat. No. 5,019,467 discloses a flexible battery comprising a flexible insulating material, a positive current collection layer, a positive active layer, a solid polyelectrolyte layer, and a thin metallic film layer as the anode. In this battery, the positive current collection layer, positive active layer, and solid polymer electrolyte layer are coated on the flexible insulating material. The thin metallic layer is formed by vacuum deposition, sputtering, ion-plating, or non-electrolytic plating (i.e., not printed).
U.S. Pat. No. 5,747,191 discloses that polymer film inks may be used to form a conductive layer (current collector) for a thin flexible battery. This battery, however, requires an anode foil, which is formed by “wave-soldering-like” method.
In U.S. Pat. No. 5,558,957, a thin flexible battery requires the use of metal foils to form the current collectors, and anode and cathode layers.
There is a need for a relatively inexpensive, thin, flexible battery with a low energy density. Such a battery could be used in transdermal delivery systems for pharmaceuticals to provide an additional driving force to facilitate the diffusion of the drug across the skin. Such a battery could be used in a skin sensor, such as those used to monitor blood sugar levels or control insulin pumps. These batteries could be used to power smart (transmitting) baggage tags, ID's, and the like. Such a battery could also be used to power certain novelty devices such as greeting cards.
Accordingly, there is a need for relatively inexpensive, thin, flexible, disposable low energy density battery.